Should I let him go?

We have been off and on for 4 years and he is the only one that has ever made me feel like my heart was beating out of my chest and still does to this day puts a smile on my face just to hear his voice or see his face I don't think I could ever be as attracted to or love someone as much as I do this man what should I do? I don't think he's ready to settle down yet I think in 6 months we can make it work and just work on ourselves until then.